Peracarida

{{Short description|Order of crustaceans}} {{Automatic taxobox | fossil_range = upper Devonian–present, {{fossil range|365|0|earliest=0}} | image = Gammarini (Gammaridea) delle alghe e della sabbia del litorale del golfo di Napoli (C. Merculiano).jpg | image_caption = Gammarid amphipods from the Gulf of Naples  | taxon = Peracarida | authority = Calman, 1904 <ref>{{cite journal |author=W. T. Calman |author-link=William Thomas Calman |year=1904 |title=On the Classification of the Crustacea Malacostraca |journal=Annals and Magazine of Natural History |volume=13 |issue=74 |pages=144–158 |url=https://zenodo.org/record/1430017 |doi=10.1080/00222930408562451}}</ref> }}

The superorder '''Peracarida'''{{Efn|New Latin; from Greek ''pēra'' (pouch, bag) + New Latin -carida (from Latin carid-, caris, a kind of sea crab)<ref>{{Cite Merriam-Webster|Peracarida|access-date=2025-06-19}}</ref>}} is a large group of malacostracan crustaceans, having members in marine, freshwater, and terrestrial habitats. They are chiefly defined by the presence of a '''''marsupium''''' (the "brood pouch"), formed from thin flattened plates (''oostegite''s) borne on the basalmost segments of the legs.

Peracarida is one of the largest crustacean taxa and includes about 12,000 species. Most members are less than {{convert|2|cm|1|abbr=on}} in length,<ref name=Ruppert/> but the largest can be quite sizeable, such as the giant isopod ''Bathynomus giganteus'' which can reach {{convert|76|cm|0|abbr=on}} in length, and the giant amphipod ''Alicella gigantea'' ({{convert|34|cm|0|abbr=on}} long). The earliest known peracaridian was ''Oxyuropoda ligioides'', a fossil taxon dated to the Late Devonian of Ireland (more than 360 mya).<ref>{{cite journal | last1=Robin | first1=N. | last2=Gueriau | first2=P. | last3=Luque | first3=J. | last4=Jarvis | first4=D. | last5=Daley | first5=A. C. | last6=Vonk | first6=R. | title=The oldest peracarid crustacean reveals a Late Devonian freshwater colonization by isopod relatives | journal=Biology Letters | publisher=The Royal Society | volume=17 | issue=6 | year=2021 | issn=1744-957X | pmid=34129798 | doi=10.1098/rsbl.2021.0226 |pmc=8205522 | article-number=20210226|biorxiv=10.1101/2021.04.25.441336}}</ref>

==Orders== There is some disagreement as to which orders should be included within Peracarida.{{Clarify|reason=What are the dissenting opinions? This page doesn't talk about them|date=June 2025}} The World Register of Marine Species WoRMS (2023) includes the following 13 orders:<ref>[https://www.marinespecies.org/aphia.php?p=taxdetails&id=1090 Peracarida] World Register of Marine Species 5 Aug 2023</ref> *Amphipoda Latreille, 1816 (scuds, sandhoppers, skeleton shrimp, whale lice, etc.) *Bochusacea Gutu & Iliffe, 1998 *Cumacea Krøyer, 1846 *Ingolfiellida Hansen, 1903 *Isopoda Latreille, 1817 (woodlice, gribbles, tongue lice, etc.) *Lophogastrida Sars, 1870 *Mictacea Bowman et al., 1985 *Mysida Haworth, 1825 (opossum shrimp) *{{Extinct}}Pygocephalomorpha Beurlen, 1930 *Spelaeogriphacea Gordon, 1957 *Stygiomysida Tchindonova, 1981 *Tanaidacea Dana, 1849 *Thermosbaenacea Monod, 1927

Of these Bochusacea, Ingolfiellida and Stygiomysida were added to the classification of Martin & Davies (2001).<ref>{{cite book |url=http://atiniui.nhm.org/pdfs/3839/3839.pdf |title=An Updated Classification of the Recent Crustacea |author1=Martin, J. W. |author2=G. E. Davis |name-list-style=amp |year=2001 |pages=132 pp |publisher=Natural History Museum of Los Angeles County |archive-date=2013-05-12 |access-date=2009-12-14 |archive-url=https://web.archive.org/web/20130512091254/http://atiniui.nhm.org/pdfs/3839/3839.pdf |url-status=dead }}</ref> Ruppert et al. (2004) excluded Thermosbaenacea and placed it in a separate order, Pancarida. They also still kept Lophogastrida, Mysida and Pygocephalomorpha in a single order Mysidacea,<ref name=Ruppert>{{cite book |title=Invertebrate Zoology, 7th edition |last1=Ruppert |first1=E. E. |last2=Fox |first2=R. S. |last3=Barnes |first3=R. D. |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |pages=651–652 }}</ref> an arrangement that was disputed by Meland and Willassen (2007) since molecular data shows that the three orders are not closely related (they do not form a clade).<ref>{{cite journal |author1=Meland, K. |author2=Willassen, E. |year=2007 |url=http://decapoda.nhm.org/pdfs/31293/31293.pdf |title=The disunity of "Mysidacea" (Crustacea) |journal=Molecular Phylogenetics and Evolution |volume=44 |issue=3 |pages=1083–1104 |pmid=17398121 |doi=10.1016/j.ympev.2007.02.009|bibcode=2007MolPE..44.1083M }}</ref>

==Description== [[File:Mandible.svg|thumb|right|upright|Generalized peracarid mandibula{{efn|1. Molar process; 2. Spine row; 3. ''Lacinia mobilis''; 4. Incisor process; 5. Palp}}]] {{Expand section|date=June 2025}} The defining characteristics of the order includes the possession of a single pair of maxillipeds (rarely 2–3), mandibles with an articulated accessory process between the molar and incisor "teeth" in the adults (called the ''lacinia mobilis''), and of carapace which is often reduced in size and is not fused with the posterior thoracic somites.<ref name="TAFI">{{cite web |url=http://www.tafi.org.au/zooplankton/imagekey/malacostraca/peracarida/ |title=Peracarida |work=Guide to the marine zooplankton of south eastern Australia |publisher=Tasmanian Aquaculture & Fisheries Institute |date=June 2008 |access-date=August 30, 2011 |archive-url=https://web.archive.org/web/20111004050244/http://www.tafi.org.au/zooplankton/imagekey/malacostraca/peracarida/ |archive-date=October 4, 2011 }}</ref> In some orders, the young hatch at a post-larval, prejuvenile stage called a ''manca'' which lacks the last pair of legs.<ref name="TAFI"/>

===Marsupium=== [[File:Livoneca redmanii (close-up of larvae in the brood pouch) (13961011896).jpg|thumb|left|''Livoneca redmanii''; Cymothoidae, young in brood pouch]] The '''''marsupium''''' of female peracaridans is a characteristic unique to this group (though males lack this part of their anatomy).<ref>{{cite book |author=Peter Ax |year=2000 |title=The Phylogenetic System of the Metazoa |series=Multicellular Animals |volume=2 |publisher=Springer |isbn=978-3-540-67406-1 |chapter=Peracarida |pages=174–178 |chapter-url=https://books.google.com/books?id=FweHI7uZ198C&pg=PA174}}</ref><ref>{{cite book |author=Sol Felty Light |year=1974 |title=Intertidal Invertebrates of the Central California Coast |edition=2nd |publisher=University of California Press |isbn=978-0-520-00750-5 |chapter=Subclass Peracarida |pages=135–171 |chapter-url=https://books.google.com/books?id=2Qnod-98-q8C&pg=PA135}}</ref> It is a space on the ventral surface of the animal which functions as a brood pouch,<ref>{{cite web |title=Marsupium |url=https://research.nhm.org/glossary/define.html?term=Marsupium |website=research.nhm.org/ |publisher=Natural History Museum of Los Angeles County » Crustacea Glossary |access-date=19 June 2025}}</ref> and is enclosed by the large, flexible ''oostegites'', which are bristly flaps (sometimes defined as ''lamellae'') which extend from the basal segments of the pereiopods (the "hip" or ''coxae''),<ref>{{cite web |title=Oostegites |url=https://research.nhm.org/glossary/define.html?term=Oostegites |website=research.nhm.org/ |publisher=Natural History Museum of Los Angeles County » Crustacea Glossary |access-date=19 June 2025}}</ref> which form the floor of a chamber "roofed" by the animal's sternum.<ref>{{cite book |author=G. C. B. Poore |year=2002 |series=Zoological Catalogue of Australia |volume=19.2A |title=Crustacea: Malacostraca. Syncarida, Peracarida: Isopoda, Tanaidacea, Mictacea, Thermosbaenacea, Spelaeogriphacea |publisher=CSIRO Publishing |isbn=978-0-643-06901-5 |chapter=Superorder: Peracarida Calman, 1905 |pages=24–25 |chapter-url=https://books.google.com/books?id=ww6RzBz42-4C&pg=PA24}}</ref> This chamber is where the eggs are brooded; females lay their eggs directly into the brood chamber, and the young will develop there, undergoing several moults before emerging as miniature adults referred to as mancae; the larval development is direct in most cases.<ref name=Ruppert/>

In the underground order Thermosbaenacea, there are no oostegites and the carapace of the female is expanded to form a dorsal marsupium.<ref name=Ruppert/>

===Manca=== '''Mancae''' ({{Singular}} '''manca'''){{efn|Derived from Latin ''mancus'', meaning "defective, imperfect."<ref>{{Cite web|url=https://lsj.gr/wiki/mancus|title=mancus - Ancient Greek (LSJ)}}</ref>}} are the post-larval stage or juvenile of the clade '''Mancoida''' which comprises all the members of the Peracarida except the Mysidacea and the Amphipoda.<ref name="Ax">{{cite book |author=Peter Ax |year=2000 |title=The Phylogenetic System of the Metazoa |series=Multicellular Animals |volume=2 |publisher=Springer |isbn=978-3-540-67406-1 |chapter=Peracarida |pages=174–178 |chapter-url=https://books.google.com/books?id=FweHI7uZ198C&pg=PA176}}</ref> Mancae closely resemble the adult form, though have not yet developed the last pair of pereiopods.<ref name="Ax"/> In some isopods, specifically the family Gnathiidae, the manca stage is a parasite of fish, and is also known as the '''praniza'''.<ref>{{cite book |author=Albert O. Bush |year=2001 |title=Parasitism: the Diversity and Ecology of Animal Parasites |publisher=Cambridge University Press |isbn=978-0-521-66447-9 |chapter=Crustacea |pages=226–241 |chapter-url=https://books.google.com/books?id=Q6Kl0FbvStoC&pg=PA235}}</ref>

==References== {{Noteslist}} {{Reflist|32em}}

== External links == *{{cite web |author=Gary Anderson |date=May 7, 2011 |url=http://peracarida.usm.edu/iwp_home.html |title=Peracarida Taxa and Literature (Cumacea, Lophogastrida, Mysida, Stygiomysida and Tanaidacea) |publisher=University of Southern Mississippi |archive-url=https://web.archive.org/web/20100124195537/http://peracarida.usm.edu/iwp_home.html |archive-date=January 24, 2010 }} *{{Wikispecies-inline}}

Category:Malacostraca Category:Crustacean superorders